Fix CVE-2020-7039:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-7039

Patches copied from upstream dependency repository:

https://gitlab.freedesktop.org/slirp/libslirp/commit/2655fffed7a9e765bcb4701dd876e9dab975f289
https://gitlab.freedesktop.org/slirp/libslirp/commit/ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9
https://gitlab.freedesktop.org/slirp/libslirp/commit/82ebe9c370a0e2970fb5695aa19aa5214a6a1c80

From 2655fffed7a9e765bcb4701dd876e9dab975f289 Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Date: Wed, 8 Jan 2020 00:58:48 +0100
Subject: [PATCH] tcp_emu: Fix oob access

The main loop only checks for one available byte, while we sometimes
need two bytes.
---
 CHANGELOG.md   | 1 +
 src/tcp_subr.c | 7 +++++++
 2 files changed, 8 insertions(+)

#diff --git a/CHANGELOG.md b/CHANGELOG.md
#index 00d0ce2..5cf94a8 100644
#--- a/CHANGELOG.md
#+++ b/CHANGELOG.md
#@@ -20,6 +20,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
# ### Fixed
# 
#  - ncsi: fix checksum OOB memory access
#+ - `tcp_emu()`: fix OOB accesses
# 
# ## [4.1.0] - 2019-12-02
# 
diff --git a/src/tcp_subr.c b/src/tcp_subr.c
index 382aa38..9c1bdec 100644
--- a/slirp/src/tcp_subr.c
+++ b/slirp/src/tcp_subr.c
@@ -871,6 +871,9 @@ int tcp_emu(struct socket *so, struct mbuf *m)
                 break;
 
             case 5:
+                if (bptr == m->m_data + m->m_len - 1)
+                        return 1; /* We need two bytes */
+
                 /*
                  * The difference between versions 1.0 and
                  * 2.0 is here. For future versions of
@@ -886,6 +889,10 @@ int tcp_emu(struct socket *so, struct mbuf *m)
                 /* This is the field containing the port
                  * number that RA-player is listening to.
                  */
+
+                if (bptr == m->m_data + m->m_len - 1)
+                        return 1; /* We need two bytes */
+
                 lport = (((uint8_t *)bptr)[0] << 8) + ((uint8_t *)bptr)[1];
                 if (lport < 6970)
                     lport += 256; /* don't know why */
-- 
2.24.1

From ce131029d6d4a405cb7d3ac6716d03e58fb4a5d9 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Thu, 9 Jan 2020 15:12:27 +0530
Subject: [PATCH] slirp: use correct size while emulating IRC commands

While emulating IRC DCC commands, tcp_emu() uses 'mbuf' size
'm->m_size' to write DCC commands via snprintf(3). This may
lead to OOB write access, because 'bptr' points somewhere in
the middle of 'mbuf' buffer, not at the start. Use M_FREEROOM(m)
size to avoid OOB access.

Reported-by: Vishnu Dev TJ <vishnudevtj@gmail.com>
Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Message-Id: <20200109094228.79764-2-ppandit@redhat.com>
---
 src/tcp_subr.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/tcp_subr.c b/src/tcp_subr.c
index 9c1bdec..ee7a938 100644
--- a/slirp/src/tcp_subr.c
+++ b/slirp/src/tcp_subr.c
@@ -763,7 +763,8 @@ int tcp_emu(struct socket *so, struct mbuf *m)
                 return 1;
             }
             m->m_len = bptr - m->m_data; /* Adjust length */
-            m->m_len += snprintf(bptr, m->m_size, "DCC CHAT chat %lu %u%c\n",
+            m->m_len += snprintf(bptr, M_FREEROOM(m),
+                                 "DCC CHAT chat %lu %u%c\n",
                                  (unsigned long)ntohl(so->so_faddr.s_addr),
                                  ntohs(so->so_fport), 1);
         } else if (sscanf(bptr, "DCC SEND %256s %u %u %u", buff, &laddr, &lport,
@@ -773,8 +774,8 @@ int tcp_emu(struct socket *so, struct mbuf *m)
                 return 1;
             }
             m->m_len = bptr - m->m_data; /* Adjust length */
-            m->m_len +=
-                snprintf(bptr, m->m_size, "DCC SEND %s %lu %u %u%c\n", buff,
+            m->m_len += snprintf(bptr, M_FREEROOM(m),
+                         "DCC SEND %s %lu %u %u%c\n", buff,
                          (unsigned long)ntohl(so->so_faddr.s_addr),
                          ntohs(so->so_fport), n1, 1);
         } else if (sscanf(bptr, "DCC MOVE %256s %u %u %u", buff, &laddr, &lport,
@@ -784,8 +785,8 @@ int tcp_emu(struct socket *so, struct mbuf *m)
                 return 1;
             }
             m->m_len = bptr - m->m_data; /* Adjust length */
-            m->m_len +=
-                snprintf(bptr, m->m_size, "DCC MOVE %s %lu %u %u%c\n", buff,
+            m->m_len += snprintf(bptr, M_FREEROOM(m),
+                         "DCC MOVE %s %lu %u %u%c\n", buff,
                          (unsigned long)ntohl(so->so_faddr.s_addr),
                          ntohs(so->so_fport), n1, 1);
         }
-- 
2.24.1

From 82ebe9c370a0e2970fb5695aa19aa5214a6a1c80 Mon Sep 17 00:00:00 2001
From: Prasad J Pandit <pjp@fedoraproject.org>
Date: Thu, 9 Jan 2020 15:12:28 +0530
Subject: [PATCH] slirp: use correct size while emulating commands

While emulating services in tcp_emu(), it uses 'mbuf' size
'm->m_size' to write commands via snprintf(3). Use M_FREEROOM(m)
size to avoid possible OOB access.

Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Message-Id: <20200109094228.79764-3-ppandit@redhat.com>
---
 src/tcp_subr.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/src/tcp_subr.c b/src/tcp_subr.c
index ee7a938..177dfd2 100644
--- a/slirp/src/tcp_subr.c
+++ b/slirp/src/tcp_subr.c
@@ -681,7 +681,7 @@ int tcp_emu(struct socket *so, struct mbuf *m)
             n4 = (laddr & 0xff);
 
             m->m_len = bptr - m->m_data; /* Adjust length */
-            m->m_len += snprintf(bptr, m->m_size - m->m_len,
+            m->m_len += snprintf(bptr, M_FREEROOM(m),
                                  "ORT %d,%d,%d,%d,%d,%d\r\n%s", n1, n2, n3, n4,
                                  n5, n6, x == 7 ? buff : "");
             return 1;
@@ -716,8 +716,7 @@ int tcp_emu(struct socket *so, struct mbuf *m)
             n4 = (laddr & 0xff);
 
             m->m_len = bptr - m->m_data; /* Adjust length */
-            m->m_len +=
-                snprintf(bptr, m->m_size - m->m_len,
+            m->m_len += snprintf(bptr, M_FREEROOM(m),
                          "27 Entering Passive Mode (%d,%d,%d,%d,%d,%d)\r\n%s",
                          n1, n2, n3, n4, n5, n6, x == 7 ? buff : "");
 
@@ -743,8 +742,8 @@ int tcp_emu(struct socket *so, struct mbuf *m)
         if (m->m_data[m->m_len - 1] == '\0' && lport != 0 &&
             (so = tcp_listen(slirp, INADDR_ANY, 0, so->so_laddr.s_addr,
                              htons(lport), SS_FACCEPTONCE)) != NULL)
-            m->m_len =
-                snprintf(m->m_data, m->m_size, "%d", ntohs(so->so_fport)) + 1;
+            m->m_len = snprintf(m->m_data, M_ROOM(m),
+                                "%d", ntohs(so->so_fport)) + 1;
         return 1;
 
     case EMU_IRC:
-- 
2.24.1

